2 = 2                          {2} 
3 = 3                          {3} 
4 = 2 x 2                      {2} 
5 = 5                          {5} 
6 = 2 x 3                      {2, 3} 
7 = 7                          {7} 
8 = 2 x 2 x 2                  {2} 
9 = 3 x 3                      {3} 
10 = 2 x 5                     {2, 5} 
11 = 11                        {11} 
12 = 2 x 2 x 3                 {2, 3} 
13 = 13                        {13} 
14 = 2 x 7                     {2, 7} 
15 = 3 x 5                     {3, 5} 
16 = 2 x 2 x 2 x 2             {2} 
17 = 17                        {17} 
18 = 2 x 3 x 3                 {2, 3} 
19 = 19                        {19} 
20 = 2 x 2 x 5                 {2, 5} 
21 = 3 x 7                     {3, 7} 
22 = 2 x 11                    {2, 11} 
23 = 23                        {23} 
24 = 2 x 2 x 2 x 3             {2, 3} 
25 = 5 x 5                     {5} 
26 = 2 x 13                    {2, 13} 
27 = 3 x 3 x 3                 {3} 
28 = 2 x 2 x 7                 {2, 7} 
29 = 29                        {29} 
30 = 2 x 3 x 5                 {2, 3, 5} 
31 = 31                        {31} 
32 = 2 x 2 x 2 x 2 x 2         {2} 
33 = 3 x 11                    {3, 11} 
34 = 2 x 17                    {2, 17} 
35 = 5 x 7                     {5, 7} 
36 = 2 x 2 x 3 x 3             {2, 3} 
37 = 37                        {37} 
38 = 2 x 19                    {2, 19} 
39 = 3 x 13                    {3, 13} 
40 = 2 x 2 x 2 x 5             {2, 5}